The present invention relates to flangeless winding cores for magnetic tape, adapted for stacking with their surfaces in contact and the tapes wound thereabout in supporting contact.
The recording of sound on magnetic tape and the packaging and marketing of such tape recordings has become a large-scale industry incorporating many mass production techniques. Standardized winding cores used in transporting the tapes and handling the tapes during processing are generally adapted to take advantage of such techniques.
Two factors are of particular importance with respect to such techniques. First, the capability to stack such cores with tape wound therearound, but without intervening support material between the tape on adjacent cores, permits increased efficiency in transporting and handling the cores and tape. Secondly, the expensive and sophisticated machinery utilized in processing the tape in large part is adapted to employ holding devices for the cores which create a significant design requirement. Briefly, to accomodate stacking efficiency, the core should generally have a height approximately equal to the width of the tape wound therearound. On the other hand, to accomodate processing with the existing expensive machinery, a greater height than the width of many of the tape sizes, is required.
Ender et al, U.S. Pat. No. 4,081,151 addresses these somewhat contradictory requirements by providing deformations which alternately rises on opposite (top and bottom) sides of a core. These deformations take a rather complex shape permitting interlocking of a deformation rising from the top side of a lower core with the recessed underside of a deformation rising from the top side of an upper core. The height of such cores, apart from the projections, may then generally be about the same as the width of the tape. With respect to such height, Ender discloses projections extending about one half of that height beyond the part of the core having the height; however, cores along the lines of that in Ender, have been employed with projections larger than this ratio. Concerning another aspect, spindle indentations normally required in the winding cores, as a result of the other aspects of the design in Ender, are located along the deformations, and follow an alternating pattern resulting from the alternating pattern of the deformation.
In another embodiment, Ender discloses a winding core with a bead-like ridge valley configuration along the top and bottom of the core; and indentations along a ridge are provided to receive pins projecting from a mating valley to prevent relative rotation of adjacent cores. This embodiment has the disadvantage, however, that the core can only be stacked one way up; that is, the elevated side of one core of the stack must always be placed in the recessed surface of the other.
The problem of satisfying and processing requirements for tape winding cores is also addressed in Schor U.S. Pat. Nos. 4,201,353 and 4,280,670, by providing an annular body having an outer circumferential surface on which the tape is wound and a center hole around which a multiplicity of recesses are uniformly distributed. A set of six opposed projections extend upwardly and downwardly from the top and bottom surfaces of the annular body, the projections being arranged in a circular array adjacent the center hole and spaced for mating with every third recess along the array of recesses of a sandwiching core. In the disclosed embodiment, the projectionms rise 2.46 mm (0.097") above the level of the top and bottom surfaces which, when added to a body thickness of 3.96 mm (0.156") gives a total height of 8.88 mm, substantially equal to the 9.9 mm (0.350") standard. In spite of its meeting this aspect of the standard, the commercial version of the Schor winding core tends to slip on the driving hub of existing processing machinery, probably because the overall height of the projections is 0.312", not 0.350" disclosed in the patent, and thus not sufficient adquately to engage the hub.
Furthermore, a flangeless winding core for magnetic tape adapted for stacking between like winding cores is addressed in Filippo U.S. Pat. No. 4,341,357, by providing an annular body with parallel top and bottom annular surfaces, an outer circumferential surface around which the tape is wound, and an inner circumferential surface from which a plurality of angularly spaced lugs extend radially inward, the inner ends of which are curved to define a discontinuous inner circumferential core surface. The lugs have the shape of a sector of an annulus, are spaced from each other by a like number of similarly shaped gaps, and project equally above the top and bottom surfaces of the annular body a distance greater than one-half the axial dimension of the annular body. The top and bottom surfaces of the lugs are parallel to each other and slope relative to the median plane of the annular body, thereby to maximize the effective axial length of the discontinuous inner circumferential core surface while permitting stacking of the annular body surfaces against one another, with the lugs mating with the gaps of a nesting core, and enabling a tape having a width approximately the same as the axial dimension of the outer circumferential surface to support the tape wound about an adjacent core when the cores are stacked.